編碼無合成器之LINC-OFDM系統:系統設計和效能分析

Abstract

正交分頻多工(OFDM)的主要缺點是傳送訊號有很高的峰值與平均功率比(peak-to-average power ratio, PAPR)，因此需要高線性度的功率放大器才能使系統操作，這使得功率放大器在RF系統中成為最耗能的一個元件。因此有研究者發展出無合成器之非線性元件線性放大(Combinerless linear-amplifica tion-with-nonlinear-component, CL-LINC)技術來解決此問題。CL-LINC系統將訊號拆解成兩路並各經由非線性放大器後，再經由兩根天線傳送，而兩路訊號會在空氣中結合並為目的端所接收。本論文旨在評估一完整之編碼CL-LINC系統之效能，我們首先建立數位和類比傳送和接收模型，其中包括有升降頻取樣、數位和類比的低通濾波器、數位/類比轉換器和非線性功率放大器。接著，我們提出一新訊號拆解法來提升編碼CL-LINC之系統效能，最後我們評估傳統OFDM系統，使用傳統訊號拆解法的編碼之CL-OFDM-LINC系統，以及使用所提訊號拆解法之CL-OFDM-LINC之效能。模擬結果顯示，編碼無合成器LINC-OFDM系統的效率遠高於傳統OFDM系統。

One of the drawbacks of OFDM systems is its high peak-to-average-power ratio (PAPR). Thus, the power amplifier (PA) requires high linearity, making it the most power hungry component in its RF system. Combinerless linear-amplification-with- nonlinear -component (CL-LINC) has been developed to solve the problem. CL-LINC decomposes the signal into two components, amplifies the decomposed signals with nonlinear PAs, and then transmits the signals with two antennas. The transmitted signals are then combined in the air and received at the destination. In this thesis, we evaluate the performance of a complete coded CL-LINC-OFDM system. First, we establish digital and analog models for signal transmission and receiving, which include upsampling/dowsampling, digital filtering, analog filtering, digital-to-analog/analog-to-digital conversion, and nonlinear PAs. Then, we propose a signal-component- separator (SCS) to improve the system performance. Finally, we evaluate the performance of conventional OFDM system, CL-LINC-OFDM with conventional SCS, and that with the proposed SCS. Simulations show that the efficiency of CL-LINC-OFDM significantly outperforms the conventional OFDM.